1. Field of the Invention
The present invention relates to magnetic disks used in hard disk drives, for example, and relates in particular to a method of manufacturing magnetic disks having micro-waviness on their surface or a method for fabricating substrates used for such a magnetic disk manufacturing method. Hereinafter, "substrate" refers not only to a base plate itself made of aluminum and glass, but also to such a substrate including any magnetic, carbon, lubricating or Ni--P layer formed on the base plate.
2. Description of the Related Art
With reference to a conventional layered structure of a magnetic disk shown in FIG. 24A, an aluminum substrate material 350 is coated with successive Ni--P layer 352, magnetic layer 354 and carbon layer 356. In response to demands for hardness and precision flatness of the substrate in recent years, a glass substrate has become commercial to replace the Al substrate material, and as shown in FIG. 24B, such a disk is comprised of successive magnetic layer 354 and carbon layer 356 coated on a surface of a glass substrate material 360.
In order to obtain a high data density, hard disk drives are used by floating a magnetic head on the disk surface at a so-called "semi-contact" state with minimum possible separation distance therefrom, so that a high precision in surface flatness is required on the disk. On the other hand, an excessively flat surface may cause head sticking, and is not desirable. For this reason, it is preferable for the disk surface to have a certain degree of fine roughness, or micro-waviness.
In conventional techniques for aluminum substrates, micro-textured structures are fabricated on a Ni--P layer formed on the substrate surface by using such mechanical methods as abrading with an abrasive tape or abrasive cloth as well as physical treatment such as laser irradiation and bombardment with high energy ions. For glass substrates, texture fabrication techniques include sputtering with hydrofluoric acid vapor or surface crystallization, in addition to laser or high energy ion irradiation.